© Michael Lacewing Plato and Hume on Human Understanding Michael Lacewing

The two camps Rationalism: we can have substantive a priori knowledge of how things stand outside the mind. Empiricism: we cannot.

‘A priori’ and ‘analytic’ A priori: knowledge that does not require (sense) experience to be known to be true (v. a posteriori) A proposition is analytic if it is true or false just in virtue of the meanings of the words.

Plato’s rationalism We have a form of rational ‘intuition’ or ‘insight’, nous, which allows us to grasp certain truths intellectually (after a lot of training!). Sense experience cannot give us knowledge, only reason can. Our concepts are derived from, or imperfect reflections of, the Forms, which are only known through reason.

The Forms exist independently Good things are not the same as goodness (Form of the Good). –If all good things were destroyed, this wouldn’t destroy goodness itself. Forms don’t exist in any particular place or time. Forms don’t change. Forms are perfect examples (nothing is more good than goodness itself).

Against empirical knowledge All objects of experience are particular things. All particular things are both one thing, e.g. large, beautiful, good, and the opposite. If something is both X and not-X, then we can’t know that it is X.

Knowledge of the Forms Particular things are what they are only relatively and transiently; knowledge is certain and permanent. The Form of beauty is pure beauty; it (alone) is not both beautiful and not beautiful. The Form of beauty is beautiful under all conditions, to all observers, at all times. Therefore, we can have knowledge of the Forms, though not through our senses.

Hume’s fork We can only have knowledge of –Relations of ideas –Matters of fact Relations of ideas are a priori and analytic Matters of fact are a posteriori and synthetic Reason doesn’t do ‘insight’.

Origins of concepts All ideas are ultimately derived from impressions – something that occurs in our experience. We can form complex ideas for which we have no corresponding impression. But all such complex ideas are derived from simple ideas, which are copies of impressions.

On reason Hume to Plato: What is ‘nous’? How does it provide knowledge? Plato to Hume: Hume shows how limited empiricism is. Without nous, we fall into scepticism.

On knowledge Even if knowledge cannot change, that doesn’t mean the object of knowledge can’t change: –I can know the size of this handout now, even if the handout changes later. –Plato has confused a property of knowledge for a property of the object of knowledge.

On certainty Plato sets the standard for knowledge very high (certainty). Hume seems to accept this - we only know immediate sensation, deductive reasoning, and analytic truth So they both agree we can’t have knowledge of physical objects!

On the Good Plato: What gives truth to the things known [the Forms] and the power to know to the knower is the Form of the Good. –What is the Good? Hume: there is no knowledge of the good. Morality isn’t about truth, but about feeling.